Alpha 1,4-N-acetylflucosaminyltransferase (Alpha4Gn-T) mediates the biosynthesis of mucin type glycoprotein (O-glycan). Alpha4Gn-T acts as the key enzyme for the formation of the unique glycan GlcNAcalpha1-4Galbeta1-R, and most efficiently transfers N-acetylglucosamine (GlcNAc) to core 2 branched O-glycans. Alpha4Gn-T is a single-pass type II membrane protein associated with the Golgi apparatus and contains the conserved DXD motif involved in catalytic activity. It is expressed in stomach and pancreas, as well as in gastric cancer cells. Alpha4Gn-T is not expressed in peripheral blood cells, making it a useful biomarker for pancreatic cancer. Alpha4Gn-T and Mucin 6 expression is upregulated in the gastric mucosa of H.pylori infected patients, which suggest the involvement of ?Gn-T in defense against H. pylori infection.